The present invention relates to a semiconductor light emitting device and a fabrication method thereof, an integral type semiconductor light emitting unit and a fabrication method thereof, an image display unit and a fabrication method thereof, and an illuminating unit and a fabrication method thereof. In particular, the present invention is suitably applied to light emitting diodes using nitride oxide type III–V compound semiconductors.
A related art light emitting diode representative of a semiconductor light emitting device as disclosed in WO02/07231 (see, for example pages 47–50, FIGS. 3 to 9), is configured by growing an underlying n-type GaN layer on a sapphire substrate, forming a growth mask having an opening at a specific position on the underlying n-type GaN layer, selectively growing a hexagonal pyramid shaped n-type GaN layer having tilt crystal planes tilted from a principal plane of a substrate on a portion, exposed from the opening of the growth mask, of the underlying GaN layer, and growing an active layer and a p-type GaN layer on the tilt crystal planes. According to such a light emitting diode, it is possible to improve the crystallinity of layers forming a device structure by suppressing the propagation of threading dislocations from the substrate side to the layers, and hence to enhance the luminous efficiency of the light emitting diode.
The above-described light emitting diode, however, has a problem. Although silicon oxide (SiO2) or silicon nitride (SiN) is generally used as the material of the growth mask for selective growth, the use of such a silicon-based material is disadvantageous in that since the selective growth of the n-type GaN layer and the subsequent growth of the p-type GaN layer are both performed at a temperature being as high as about 100° C., silicon (Si) and oxygen (O) are released from the surface of the growth mask and incorporated in a portion, closed to the growth mask, of the growing layer upon growth of the GaN layers. The phenomenon becomes significant, particularly, at the time of growth of the p-type GaN layer. In this case, if Si functioning as an n-type impurity against GaN is incorporated in the growing layer at the time of growth of the p-type GaN layer, it is hard to ensure the p-type conduction of the p-type GaN layer, and even if the p-type conduction of the p-type GaN layer is ensured, the concentration of positive-holes and the mobility are both significantly reduced. This obstructs the improvement in luminous efficiency of the light emitting diode.
Another problem of the above-described related art light emitting diode is as follows. In the photolithography step required for forming the opening of the growth mask, a resist is brought into close-contact with a mask plane, followed by partial removal of the resist. In this removal of the resist, the resist is liable to remain in micro-gaps of the growth mask. Such a resist remaining in the micro-gaps is hard to be removed. As a result, at the subsequent growth at a high temperature, the remaining resist acts as an impurity source, tending to degrade characteristics of the GaN layers, particularly, the p-type GaN layer.